HD 660S2 – It's Sennheiser's revised €599 classic with the promise of more potent LF. Technical changes apply to a finer voice coil, altered compliance of the driver surround and optimized airflow behind the driver. These improvements claim extra bass reach and more precise impulse response. Included are 180cm cables with 6.3mm and 4.4mm plugs plus a 3.5mm adapter and carrying case. Not changed is the 300Ω impedance.
